a Black Hole?
to the general theory of relativity, a black hole is a region
of space from which nothing, including light, can escape. It is
the result of the denting of spacetime caused by a very compact
mass. Around a black hole there is an undetectable surface which
marks the point of no return, called an event horizon. It is called
"black" because it absorbs all the light that hits it, reflecting
nothing, just like a perfect black body in thermodynamics. Under
the theory of quantum mechanics black holes possess a temperature
and emit Hawking radiation through slow dissipation by anti-protons.
undetectable interior, a black hole can be observed through its
interaction with matter. A black hole can be inferred by tracking
the movement of a group of stars that orbit a region in space.
Alternatively, when gas falls into a stellar black hole from a
companion star or nebula, the gas spirals inward, heating to very
high temperatures and emitting large amounts of radiation that
can be detected from earthbound and Earth-orbiting telescopes.
have identified numerous stellar black hole candidates, and have
also found evidence of supermassive black holes at the center
of every galaxy. After observing the motion of nearby stars for
16 years, in 2008 astronomers found compelling evidence that a
supermassive black hole of more than 4 million solar masses is
located near the Sagittarius A* region in the center of the Milky
Black Holes Formed?
holes are made when a giant star, called a supergiant, at least
twenty times bigger than our own Sun dies, and leaves behind a
mass that is at least one solar mass. Stars die when they run
out of hydrogen or other nuclear fuel to burn and start to collapse.
star's death is called a supernova. Stars are usually in equilibrium,
which means they are making enough energy to push their mass outward
against the force of gravity. When the star runs out of fuel to
make energy, gravity takes over. Gravity pulls the center of the
star inward very quickly (so quickly that it would have to be
repeated several thousand times before it took up a single second),
and it collapses into a little ball. The collapse is so fast and
violent that it makes a shock wave, and that causes the rest of
the star to explode outward. As the gravity pushes the star inward,
the pressure in the center of star reaches to such an extreme
level that it enables heavier molecules like iron and carbon to
interact to release nuclear energy. The release of the energy
from the star during a very short period of time (about one hour)
is with such a high rate that it outshines an entire galaxy.
The ball in
the center is so dense (a lot of mass in a small space, or volume),
that if you could somehow scoop only one teaspoon of material
and bring it to Earth, it would sink to the core of the planet.
If the original star was large enough the densely packed ball
is called a singularity, the core of a black hole, but if it was
not it would become either a neutron star or a dwarf star. Even
without a supernova, a black hole will form any time there is
a lot of matter in a small space, without enough energy to act
against gravity and stop it from collapsing. If supernovas are
so bright, why do we not see them often? Actually, there are usually
hundreds of years between naked-eye super nova sightings. It is
because the period of being a super nova in a star life cycle
is only a few hours out of the billions of years in a star's life
span. The probability (chance) of looking at a star in sky and
that being in super nova state is equal to the ratio of an hour
over several billion years.
It is worth
mentioning that all of the heavier materials like carbon, oxygen,
all the metals, etc, that make the life on the earth possible
and are ingredients of all living creatures, can only form in
the extreme pressure at the center of a super nova. So we are
all a remnant ash from one exploding star several billion years
have also been found in the middle of every major galaxy in the
universe. These are called supermassive black holes, and are the
biggest black holes of all. They formed when the Universe was
very young, and also helped to form all the galaxies.
holes are also responsible for making things called quasars. A
quasar occurs when a black hole consumes all the gas surrounding
it. As the gas gets close to the black hole itself, it heats up
from a process called friction, and glows so brightly that this
light can be seen on the other side of the Universe. It is often
brighter than the whole galaxy the quasar is in. When astronomers
first found quasars, they thought they had found objects close
to us. After using a measuring technique called red shift, they
discovered these quasars were actually very far away in the universe.
a wormhole is a hypothetical topological feature of spacetime
that would be, fundamentally, a "shortcut" through spacetime.
A wormhole is, in theory, much like a tunnel with two ends each
in separate points in spacetime. In 1935, Albert Einstein and
Nathan Rosen in 1935 first dreamed up the idea of a wormhole.
They realized that general relativity allows the existence of
“bridges,” originally called Einstein-Rosen bridges but now known
as wormholes. These space-time tubes act as shortcuts connecting
distant regions of space-time.
below that shows how a wormhole connects black holes with white
There is no
observational evidence for wormholes, but on a theoretical level
there are valid solutions to the equations of the theory of general
relativity which contain wormholes. But, assuming that general
relativity is correct, there may be wormholes.
A white hole,
in general relativity, is a hypothetical region of spacetime which
cannot be entered from the outside, but from which matter and
light may escape. In this sense it is the reverse of a black hole,
which can be entered from the outside, but from which nothing,
including light, may escape. (However, it is theoretically possible
for a traveler to enter a rotating black hole, avoid the singularity,
and travel into a rotating white hole which allows the traveler
to escape into another universe.) White holes appear in the
theory of eternal black holes. In addition to a black hole region
in the future, such a solution of the Einstein equations has a
white hole region in its past. However, this region does not
exist for black holes that have formed through gravitational collapse,
nor are there any known physical processes through which a white
hole could be formed.
holes, white holes have properties like mass, charge, and angular
momentum. They attract matter like any other mass, but objects
falling towards a white hole would never actually reach the white
hole's event horizon (though in the case of the maximally extended
Schwarzschild solution, discussed below, the white hole event
horizon in the past becomes a black hole event horizon in the
future, so any object falling towards it will eventually reach
the black hole horizon).
theories suggesting that white holes create new universes from
matter originating in another universe's black hole.
to a mind-bending new theory, a black hole is actually a tunnel
between universes—a type of wormhole. The matter the black
hole attracts doesn't collapse into a single point, as has
been predicted, but rather gushes out a "white hole" at the
other end of the black one, the theory goes. ..[Reference]
ARE BLACK HOLES AND WHITE HOLES CONNECTED VIA A WORMHOLE
bridges like the one visualized above have never been observed
in nature, but they provide theoretical physicists and cosmologists
with solutions in general relativity by combining models
of black holes and white holes
and Credit: Our
universe at home within a larger universe?
by AllenMcC (Creative Commons Attribution Sharealike 3.0)
KNOWLEDGE OF THE MATERIAL